How to manage or execute the piece code when portfolio/feature is updated on few fields (ex summary, calculated fields. etc)

I have requirement to execute the few rest calls when portfolio/feature is updated on few fields (ex summary, calculated fields. etc)Is there any events which supoorts or how can add custom page/panel to feature page?

You do not get access to the database. The lowest entry point for users in the RESTful Web services API. The only trigger you can put in is to create an app that does it. If you want to have something embedded in the Rally UI for your users to make use of, then you would need to implement something in JavaScript and embed it into a Custom HTML app from the catalog. If you wanted to do something outside of Rally, then you can do anything you like in the language/tool of your choice and squirt the updates into Rally.

There is no way to intercept the behaviour of the standard apps. If you wish to have a particular behaviour (or workflow), some (most) of the apps have the source code available on github.com (https://github.com/RallyApps/app-catalog), which you can modify to your needs. You will need to create your own page, add a Custom HTML app (from the app catalog) and put your modified code in there. This process is described in the help pages available through the links when you click on your avatar in the top right hand corner of the UI.

In the future, there may be an implementation of webhooks which will activate callbacks when things happen in Rally. This would give more flexibility, but is not here just yet.

one approach I would like to do if possible: Write a update trigger on the table which intern call the java class/any programing language(Service). That service can call/update the data on jira. if this is feasable approach. please update the below information.

can we know the databae?what tables are going to update on portpolio/feature?

You do not get access to the database. The lowest entry point for users in the RESTful Web services API. The only trigger you can put in is to create an app that does it. If you want to have something embedded in the Rally UI for your users to make use of, then you would need to implement something in JavaScript and embed it into a Custom HTML app from the catalog. If you wanted to do something outside of Rally, then you can do anything you like in the language/tool of your choice and squirt the updates into Rally.